Crystal calibrator harmonic selector and amplifier circuit



Jan. 1, 1929 v R. H. WORRALL CRYSTAL CALIBRATOR HARMONIC SELECTOR AND AMPLIFIER CIRCUIT Filed Oct. 28, 1927 2 Sheets-Sheet l IAMWVI. 3

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gwuawtoz Jan" 1, 1929. 1,696,933

R. H. WORRALL CRYSTAL CALIBRATOR HARMONIC SELECTOR AND AMPLIFIER CIRCUIT Filed Oct. 28, 1927 2 Sheets-Sheet 2 I B0561? 17 [461714 ZZ; m1?

Patented Jan. 1, 192a UNITED STATES I 1,696,933 PATENT OFFICE.

ROBERT WORRALL, OF WASHHTGTON, DISTRICT OF COLUMBIA, ASSIGNOB TO WIRED RADIO, INC OF NEW YORK, '11. Y., A CORPORATION OF DELAWARE.

cnYsrAI. omnaron mnmonlc snnncron AND AMPLIFIER cmcurr.

Application filed October as, 1927. Serial No. 229,481.

My invention relates broadly to harmonic selector circuits and more particularl to a circuit arrangement for a piezo e ectric crygtal controlled calibrator system and amli er. P One of the objects -of my invention is to provide a circuit arrangement for a crystal calibrator harmonic selector and amplifier wherein the particular harmonic which is being utilized may be readily determined.

Another object of my invention is to provide a coupling system between the output circuit of the piezoelectric crystal controlled oscillator and a detector system of such character that the particular harmonic to which the circuit responds may be readily selected without the necessity of resorting to a wave or frequency meter.

Other and further objects of my invention reside in the circuit arrangements described in the specification hereinafter fol lowing by reference to the accompanying drawings wherein:

Figure 1 shows diagrammatically the crystal calibrator circuit of my invention; Fig. 2 is a modified wiring diagram of a crystal calibrator embodying my invention; Fig. 3 shows the princi le of my invention as applied to a con uctive-capacitive coupling system between 'a crystal controlled oscillator and a detector; and Fig. 4 shows the application of the calibrator circuits of my invention to a measuring device for incoming signaling frequency in a signal receiving circuit.-

In crystal calibrator circuits the harmonics of a crystal fundamental frequencyare enerated' in the plate circuit inductance 0 an electron tube stem, and the beats resulting from another frequency heterodyning with a harmonic can be detected and amplified throu h the medium of a detector and audio ampli er attached .for calibration purposes.

In prior types of crystal calibrator circuits the harmonics have been impressed upon an untuned grid circuit of a detector tube. Thesetypes of calibrators while obtaining the desired results have the disadvantage of the operator not knowing which harmonic he is listening to nor what the frequency is unless the apparatus has been previously calibrated.

If the apparatus had never been calibrated it would be necessary to resort to the use of some calibrated wave meter or frequency meter at least once for each coil calibrated and preferably calibration should be oftener.

In the circuit arrangement of my invent1on I provide a detector circuit for a crystal controlled calibrator wherein the detector has a tuned grid system and the operator can tell at a glance just what harmonic he is on by reference to the condenser setting and the position of the tap on the associated inductance.

Figure 1 of the drawings shows three circults; a. crystal oscillating circuit 1, a detector circuit 2 and an amplifier circuit 3.

The crystal circuit includes the quartz crystal 4 which is the frequency control for tube system 1; a grid leak 5; a by-pass condenser (land an inductance 7 connected in the tube circuits with batteries A and B in the manner shown.

' The detector circuit 2 consists of a grid circuit including a tappedinductance 8, a variable condenser 9 and a. grid condenser 10 shunted by a grid leak 11. A coupling lead 25 and condenser 12 are connected to the grid circuit as shown; and the plate circuit which includes the primary of an audio frequency transformer 14 is shunted by a condenser 15 connected to the tube circuit and battery as shown.

Fig. 2 is a modification of Fig. 1 showing how a parallel feed circuit 17 to the oscillator plate circuit may be supplied, and also show- .ing a different method of grid leak return and how the condenser 10acts both as a grid condenser and a control device by reason of its variable properties.

Figure 3 is another modification of Fig. 1 whereby the coupling from the crystal circuit to the grid circuit of the detector tube 2 through the medium of coils 7 and 8 is eliminated and a method of conductive-capacitive coupling is used whereby condenser 9 in this casetunes a part, or all, as the case may be, of inductance 7 and this tuned circuit coupled to the grid ofthe detector tube 2 through the condenser 10, which also functions as a grid condenser. 6 indicates a bypass condenser across the B battery, 11 shows a grid leak or any method of grid bias, and 12 rep esents the coupling condenser as describ in Fig. 1.

Figure 4 contains an auxiliary circuit for the reception of weak signals from a distant That is, the radio frequency amplifier signal receiving circuit 18 may connect transferred by means nearly the same as the crystal with antenna 19 and tunin condenser 20. The radio frequency 'ampli er constituting the receiving circuit includes in its output the coil 21 and condenser 22. The remainder ofv the detector circuit is the same as in Fig. 1. Condenser 23 is a coupling condenser for coupling coil 7 to the detector tube circuit.

In the drawings the quartz crystal 4 is so chosen that its harmonics fall close enou h together to give a suflicient number of different operating frequencies. Coil 7 is of such a value that the crystal will oscillate and at the same time the coil itself will be rich in the required harmonics. This means the coil 7 must have a large inductance to capacity ratio. Any of the'common methods of grid bias such as the grid leak 1L or a choke and negative biasing'battery may be used to maintain the grid at the proper operatin potential to give a distorted wave form whic results in the harmonics.

In Figures 1 and 2 these harmonics are of inductive coupling to the inductance 8, the circuit consisting of a coil 8 and variable condenser 9, hereinafter referred to as the detector grid circuit, which may be tuned to any harmonic of the crystal fundamental frequency.

The coupling post or lead 25 brings in any radio frequency impressed upon it throu h the condenser I2 to the grid circuit of the (Fe tector tube 2. If the incoming1 generation of required armonic frequency to which the grid-circuit is tuned, these two frequencies will produce a beat which is the difference between the two frequencies which beat will be impressed upon the grid of the detector tube, 2, and the resultin audio frequency amplified through the medium of one or more stages of audio amplification 3 r and then transferred to telephones 16 or to a visual indicating device for noting the beat frequency.

In Figure 3.the harmonics are selected by tuning a part of coil 8 with the condenser 9 and transferring the harmonic to the grid of the detector 2 through the medium of condenser 10, which functions both as a grid condenser and a coupling condenser.

In Figure 4 the harmonic selection is done on the incoming frequency and not on the crystal frequency through the inductive couplmg between coils 21 and 8. The tapped coil 7 in this case assists in controlling the strength of the crystal frequency impressed u on the detector tube 2 through the medium 0 the coupling condenser 23.

here are a number of advantages arising out of the use of this type of circuit, among which may be mentioned: K

(a) The ability to select and amplify harmonic of the crystal with a knowle what thatharmonic frequency is;

,b oscillating receiver,'transmitter or any go of frequency is mitter on the harmonic either side of thegiven frequency, directly, without having to go through the medium of a receiver. I

(e) In the present type of crystal calibrator circuits the resulting audio frequency si nal is sometimes very weak, while with the armonic selector circuit this signal strength is greatly increased.

ed whereby specific desired harmonics, provided they are known to be present in the plate inductance of the crystal calibrator circuits, regardless of the method used to secure a distorted wave form in the plate circuit, can be selected and transferred to a detector circuit, whereby the beat resulting from another frequency heterodyning with the harmonic may be detected and amplified.

While I have described my invention in certain preferred embodiments, I desire that it be understood that modifications may be 'made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

at I claim as new and desire to secure by Letters Patent of the United States is as follows:

l 1. In a harmonic selector and amplifier "systems, a piezo electric crystal element, a thermionic tube circuit connected with said piezo electric crystal element and arranged to generate harmonics of the fundamental frequency of said piezo electric crystal ele ment, a detector tube circuit coupled with monic selector and amplifier system, a piezo electric crystal element, a thermionic tube By use of my invention a means is providcircuit for generating harmonics of the fundamental frequency of said piezo electric crystal element, a circuit comprising means for selecting, detecting and amplifying a selected harmonic frequency coupled with said electron tube circuit and callbrated in terms of the harmonic frequencies of the fundamental frequency of said piezo electriccrystal element, means connected to said second-mentloned c1rcu1t for lmpressinga radio tric crystal element selector and amplifier system comprising a piezo electric crystal element, a thermionic tube circuit connected with said piezo elec and arranged to generate harmonics of the fundamental frequency of said piezo electric crystal element, a circuit comprising means for selecting, detecting and amplifying a selected harmonic frequency coupled with said thermionic tube circuit and calibrated in terms of the harmonic frequencies of said piezo electric crystal element, and means for impressing current of unknown frequency upon said last mentioned circuit from a circuit whose frequency characteristic is to be determined for observing 'a beat frequency between the selected harmonic and the unknown frequency.

4. In a crystal controlled calibrator harmonic selector and amplifier circuit, a piezo electric crystal element, a thermionic tube circuit connected with said piezo electric crystal element for generating predetermined harmonics of the fundamental frequency of said piezoelectric crystal element, a tuned circuit coupled with said thermionic tube cir-' circuit for deriving a beat frequency with a selected harmonic of the fundamental frequency ofsaid piezo electric crystal element.

-5. In a crystal controlled calibrator harmonic selector and amplifier circuit, a piezo electric crystal element, a thermionic tube circuit connected with said piezo electric crystal element for generating selected harmonics of the fundamental frequency of said piezo electric crystal element, a tuned circuit comprising an inductance and a variable capacity connected with said thermionic tube circuit and adjustable to be in resonance with any selected harmonic frequency of the fundamental frequency of said piezo electric crys-' tal element, a detecting and amplifying sys-i tem connected with said tuned circuit and means connected .to said tuned circuit for receiving high frequency oscillations, the frequency of which is to be determined and deriving a beat frequency with respect to a selected harmonic for actuaitin said detecting and amplifying system and etermining the frequency of the current thus impressed upon said tuned circuit,

ROBERT H.- WORRALL. 

